Radiation protection is essential for humans to live and work safely in space. The goal of NASA's Radiation Health Program is to achieve human exploration and development of space without exceeding acceptable risk from exposure to ionizing radiation. Legal, moral, and practical considerations require that NASA limit post flight risks incurred by humans living and working in space to "acceptable" levels.

The Space Radiation Analysis Group (SRAG) at the Johnson Space Center is responsible for ensuring that the radiation exposure received by astronauts remains below established safety limits. To fulfill this responsibility, the group provides:

Evaluation of radiological safety with respect to exposure to isotopes and radiation producing equipment carried on the spacecraft.

Comprehensive crew exposure modeling capability.

Radiation instruments to characterize and quantify the radiation environment inside and outside the spacecraft.

NASA adheres to a policy known as ALARA (As Low As Reasonably Achievable); this policy recognizes that any radiation exposure results in some risk, and therefore must be minimized. Implementing ALARA is the primary basis for real-time radiological support, and understanding and minimizing exposures from space weather events is a key to that implementation.